Liquid crystal display device

ABSTRACT

In one embodiment, an array substrate includes an active area in the shape of a rectangle, and first, second third and fourth end portions, surrounding the active area. A source control circuit is electrically connected with one end of the source lines drawn to the third end portion from the active area. First and second common terminals of a common potential are formed in the first end portion. A power supply line is electrically connected with the first common terminal and extends along the second, third and fourth end portions in this order, and connected with the second common terminal. A branch wiring is electrically connected with an intermediate portion of the electric power supply line and the source control circuit, and extending in the first direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2012-072225 filed Mar. 27, 2012,the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a liquid crystaldisplay device.

BACKGROUND

A liquid crystal display device is used in various fields of OAequipments such as a personal computer and a television set, takingadvantage of the features such as light weight, thin shape, and lowpower consumption. In recent years, the liquid crystal display device isused also as displays for a portable remote terminal such as a cellularphone and PDA (personal digital assistant), a car navigation equipment,and a game machine.

In a process for manufacturing the liquid crystal display device, ameasure against static electricity is indispensable. For example, thereis a possibility that the static electricity generated in themanufacturing process or invaded from the outside gives damage tocircuits containing various wirings and switching elements in an activearea. Various techniques for improving tolerance over such staticelectricity are reviewed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute aportion of the specification, illustrate embodiments of the invention,and together with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a figure schematically showing a structure of a liquid crystaldisplay device according to one embodiment.

FIG. 2 is a figure schematically showing a structure and the equivalentcircuit of a liquid crystal display panel shown in FIG. 1 according tothe embodiment.

FIG. 3 is an enlarged figure showing a power supply line and a branchwiring in a circumference of a corner portion C2 in an array substrate.

FIG. 4 is a cross-sectional view schematically showing the structure ofthe liquid crystal display panel shown in FIG. 2.

FIG. 5 is a cross-sectional view schematically showing the structure ofthe array substrate taken along line A-B shown in FIG. 3.

DETAILED DESCRIPTION

A liquid crystal display device according to an exemplary embodiment ofthe present invention will now be described with reference to theaccompanying drawings wherein the same or like reference numeralsdesignate the same or corresponding portions throughout the severalviews.

According to one embodiment, a liquid crystal display device includes: afirst substrate including an active area in the shape of a rectanglehaving a first end portion, a second end portion, a third end portionand a fourth end portion surrounding the active area; a second substratefacing the first substrate; and a liquid crystal layer held between thefirst substrate and the second substrate; wherein the first substrateincludes; a gate line extending in a first direction and a source lineextending in a second direction orthogonally crossing the firstdirection in the active area, a source driver electrically connectedwith one end of the source lines drawn to the first end portion from theactive area, a source control circuit electrically connected with theother end of the source lines drawn to the third end portion from theactive area, a first common terminal and a second common terminal of acommon potential formed in the first end portion, a power supply lineelectrically connected with the first common terminal and extendingalong the second, third and fourth end portions in this order, andconnected with the second common terminal, and a branch wiringelectrically connected with an intermediate portion of the electricpower supply line along the third end portion and the source controlcircuit, and extending in the first direction.

FIG. 1 is a figure schematically showing a structure of a liquid crystaldisplay device according to one embodiment.

A liquid crystal display device 1 is equipped with a liquid crystaldisplay panel LPN of an active-matrix type, a driving IC chip 2connected to the flexible printed circuit board 3, etc.

The liquid crystal display panel LPN is equipped with a rectangulararray substrate AR (first substrate), a rectangular counter substrate CT(second substrate) facing the array substrate AR and a liquid crystallayer LQ held between the array substrate AR and the counter substrateCT. The liquid crystal display panel LPN is equipped with an active areaACT which displays images. The active area ACT is constituted by aplurality of pixels PX in a square form, for example, and arranged inthe shape of a matrix of a plurality of pixels PX (“m” and “n” arepositive integers).

The array substrate AR has an extending area ARE extending to outsidebeyond an end CTE of the counter substrate CT. The driving IC chip 2 andthe flexible printed circuit board 3 function as a signal source forsupplying signals required for the driving of the pixel PX and mountedin the extending area ARE of the array substrate AR.

FIG. 2 is a figure schematically showing a structure and the equivalentcircuit of a liquid crystal display panel shown in FIG. 1 according tothe embodiment.

The Array substrate AR includes a first end portion E1, a second endportion E2, a third end portion E3, and a fourth end portion E4surrounding the rectangular active area ACT. The first end portion E1and the third end portion E3 counter mutually and extend along the firstdirection X, respectively. The second end portion E2 and the fourth endportion E4 counter mutually in a second direction Y that perpendicularlyintersects in the first direction X. The first end portion E1 is locatedin the extending portion ARE. The second end portion E2, the third endportion E3, and the fourth end portion E4 counter with the countersubstrate CT.

The array substrate AR is equipped with “n” gate lines G (G1-Gn), “n”auxiliary capacitance lines C (C1-Cn), “in” source lines S (S1-Sm),etc., in the active area ACT. The gate line G and the auxiliarycapacitance line C linearly extend in the first direction X,respectively. The source lines S cross with the gate line G and theauxiliary capacitance line C through an insulating layer and extendlinearly in the second direction Y.

Each gate line G is pulled out to the outside of the active area ACT andconnected to a gate driver GD. Each auxiliary capacitance line is pulledout to the outside of the active area ACT and connected to a voltageimpressing portion CD for impressing the auxiliary capacitance voltage.The respective source lines are pulled out to the outside of the activearea ACT. One end of the respective source lines which are pulled out tothe first end E1 portion from the active area ACT is connected to asource driver SD. Another end of the respective source lines which arepulled out to the third end portion E3 from the active area ACT isconnected to a source control circuit CC. The gate driver GD, the sourcedriver SD, and the source control circuit CC are formed in the arraysubstrate AR

The pixel electrode PX includes a switching element SW, a pixelelectrode PE, and a common electrode CE. The switching element SW andthe pixel electrode PE are formed in the array substrate AR. The commonelectrode CE may be arranged in the array substrate AR or the countersubstrate CT. Retention capacitance Cs is formed between the pixelelectrode PE and the auxiliary capacitance line C.

The switching element SW is constituted by an n channel type thin filmtransistor (TFT), for example. The switching element SW is electricallyconnected with the gate line G and the source line S. The switchingelement SW may be either a top-gate type or a bottom-gate type. Thoughthe semiconductor layer is formed of poly-silicon in this embodiment,the semiconductor layer may be formed of amorphous silicon.

The pixel electrode PE is arranged in each pixel PX and electricallyconnected with the switching element SW. The common electrode CE isarranged in common to the plurality of pixel electrodes PE through theliquid crystal layer LQ. The pixel electrode PE and the common electrodeCE are formed by light transmissive materials, such as Indium Tin Oxide(ITO), Indium Zinc Oxide (IZO), etc.

Moreover, the array substrate AR includes a plurality of terminals T, apower supply line CL, a branch wiring LA, etc., outside of the activearea ACT. The plurality of terminals T is formed in the extending areaARE of the array substrate AR for connecting the flexible printedcircuit board 3. Common terminals T1 and T2 of common potential arecontained in the terminals T. The power supply line CL is formed alongwith an outermost periphery of the array substrate AR and connected withthe common terminals T1 and T2, for example. The power supply line CLfunctions as an electric supply line which supplies common potential ora guard ring, and electrically connected with the common electrode CE,etc.

In this embodiment, one end of the power supply line CL is connectedwith the common terminal T1 and extending along the second end portionE2, the third end portion E3, and the fourth end portion E4 in thisorder, and the other end is connected to the common terminal T2. Thepower supply line CL located in the second end portion E2 extends alongthe second direction Y. The power supply line CL located in the thirdend portion E3 extends along the first direction X. The power supplyline CL located in the fourth end portion E4 extends along the seconddirection Y. Moreover, the power supply line CL is formed in the shapeof a curved line or circle at a corner C1 where the second end portionE2 and the third end portion E3 cross, and a corner C2 where the thirdend portion E3 and the fourth end portion E4 cross.

The branch wiring LA is the wiring branched from an intermediate portionCLM of the power supply line CL. The branch wiring LA extends along thefirst direction X between the power supply line CL located in the thirdend portion E3 of the array substrate AR and the source control circuitCC, and electrically connected with the intermediate portion CLM of thepower supply line CL and the source control circuit CC.

In this embodiment, the intermediate portion CLM is locatedsubstantially in the center between the corner C1 and the corner C2. Thebranch wiring LA is formed extending from both positions close to thecorner C1 and the corner C2 to the substantially center portion betweenthe corner C1 and the corner C2, respectively. That is, the positionwhich electrically connects the power supply line CL with the branchwiring LA is a position apart from the corner C1 and the corner C2. Oneend portion of the branch wiring LA and the intermediate portion CLM ofthe power supply line are electrically connected by a bridge B1.Moreover, the other end portion of the branch wiring LA and a drawingwiring LB pulled out from the source control circuit CC are electricallyconnected by a bridge B2.

The power supply line CL and the branch wiring LA are explained indetail referring to FIG. 2 and FIG. 3. FIG. 3 is an enlarged view of thebranch wiring LA on a side close to the corner C2 of the array substrateAR, and only structures required for explanation are illustrated here.

The ranch wiring LA linearly extends in a straight line along the firstdirection X and includes one end portion LA1 and the other end portionLA2. The one end portion LA1 is located near the intermediate portionCLM of the power supply line CL. The other end portion LA2 is locatednear the curved portion CLC of the power supply line CL.

The branch wiring LA is equipped with a first projection P1 projectingtoward the power supply line CL. The first projection P1 is integrallyformed with the branch wiring LA. In this embodiment shown in thefigure, the first projection P1 is formed in one end portion LA1 and theother end portion LA2 of the branch wiring LA, respectively. That is,the first projection P1 is formed in the both sides which sandwich thebridge B1 in the one end portion LA1. Moreover, in the other end portionLA2, the first projection P1 is formed near the bridge B2. The firstprojection P1 extends along the second direction Y toward the powersupply line CL, and forms a sharp tip portion PP1. That is, as shown byenlarging in FIG. 3, the tip portion PP1 is formed approximately in theshape of a triangle.

The power supply line CL is equipped with a second projection P2projecting toward the first projection P1. The second projection P2 isintegrally formed with the power supply line CL. In this embodiment, thesecond projection P2 is formed near the intermediate portion CLM and thecurved portion CLC, respectively. That is, in the intermediate portionCLM, the second projection P2 is formed in the both sides which sandwichthe bridge B1 and faces the first projection P1, respectively. Moreover,the second projection P2 also counters with the first projection P1 nearthe curved portion CLC. The second projection P2 extends along thesecond direction Y toward the branch wiring LA and includes a sharp tipportion PP2. The tip portion PP2 is formed approximately in the shape ofa triangle.

The first projection P1 and the second projection P2 are located on thesame straight line in the second direction Y. Moreover, the tip portionPP1 of the first projection P1 is arranged apart from the tip portionPP2 of the second projection P2 with a gap, and apex angles thereofcounter each other.

Common potential is supplied to the source control circuit CC throughthe power supply line CL, the bridge B1, the branch wiring LA, thebridge B2, and the drawing wiring LB. The source control circuit CCfunctions as an afterimage compensation circuit. When power supply isturned off, the source control circuit CC impresses common potential toall the source lines S. At the time of the power supply OFF, a controlsignal which changes the switching element SW into an ON state issupplied to all the gate lines G. For this reason, the common potentialis written in the pixel electrode PE of each pixel PX in the active areaACT through the switching element SW. In this time, if the commonpotential is also impressed to the common electrode CE, since thepotential difference of the pixel electrode PE and the common electrodeCE becomes substantially zero, electric field currently impressed to theliquid crystal layer LQ is reset, and the afterimage can be canceled.

FIG. 4 is a cross-sectional view schematically showing the structure ofthe liquid crystal display panel shown in FIG. 2.

The array substrate AR is formed using a first insulating substrate 20which has light transmissive characteristics, such as a glass substrateand a plastic substrate. The array substrate AR includes the switchingelement SW, the pixel electrode PE, etc. The switching element SW shownhere is a thin film transistor of a bottom gated-type. The gateelectrode WG of the switching element SW is formed on the firstinsulating substrate 20 with the gate line G. The gate electrode WG iselectrically connected with the gate line G and integrally formed withthe gate line G in this embodiment. The gate electrode WG is coveredwith a first insulating layer 21. The first insulating layer 21 isarranged also on the first insulating substrate 20.

The semiconductor layer SC of the switching element SW is formed of theamorphous silicon, for example. The semiconductor layer SC is formed onthe first insulating layer 21 and located on the gate electrode WG. Asource electrode WS and a drain electrode WD of the switching element SWare formed on the first insulating layer 21, and at least one portionthereof is in contact with the semiconductor layer SC, respectively. Thesource line S is formed on the first insulating layer 21. The sourceelectrode WS is electrically connected with the source line S andintegrally formed with the source line S in this embodiment. The sourceelectrode WS and the drain electrode WD are covered with a secondinsulating layer 22 with the source line S. Moreover, the secondinsulating layer 22 is arranged also on the first insulating layer 21.

The pixel electrode PE is formed on the second insulating layer 22. Thepixel electrode PE is in contact with the drain electrode WD through acontact hole which penetrates the second insulating layer 22. The pixelelectrode PE and the second insulating layer 22 are covered with a firstalignment film 23.

On the other hand, the counter substrate CT is formed using a secondinsulating substrate 30 which has light transmissive characteristics,such as the glass substrate and the plastic substrate. The countersubstrate CT includes a black matrix 31, a color filter layer 32, etc.,on the second insulating substrate 30 facing the array substrate AR.Moreover, the counter substrate CT is equipped with a common electrodeCE in this embodiment.

The black matrix 31 is formed between adjoining pixels PX in the activearea ACT, and counters various wiring portions such as the switchingelement SW, the gate line G, the source line S formed on the arraysubstrate AR. The color filter layer 32 is arranged in each pixel PXdivided by the black matrix 31 in the active area ACT. A portion of thecolor filter layer 32 overlaps with the black matrix 31.

In the active area ACT, the common electrode CE is formed on the colorfilter layer 32 facing the array substrate AR and counters the pixelelectrode PE of each pixel PX through the liquid crystal layer LQ. Thecommon electrode CE is covered with a second alignment film 33.

The array substrate AR and the counter substrate CT as mentioned aboveare arranged so that the first alignment film 23 faces the secondalignment film 33. At this time, a spacer, for example, a pillar-shapedspacer integrally formed in one of the substrates by resin material isarranged between the array substrate AR and the counter substrate CT.Thereby, a predetermined cell gap is formed.

The liquid crystal layer LQ is enclosed in the cell gap as mentionedabove. That is, the liquid crystal layer LQ is constituted by liquidcrystal composite held between the pixel electrode PE of array substrateAR and the common electrode CE of the counter substrate CT.

Regarding the liquid crystal mode, there is no restriction inparticular. In addition, the modes which mainly use vertical electricfield or slanting electric field such as TN (Twisted Nematic) mode, OCB(Optically Compensated Bend) and VA (Vertical Aligned) mode, or themodes which mainly use lateral electric field, such as IPS (In-PlaneSwitching) mode and FFS (Fringe Field Switching) mode, are applicable.In the mode using the lateral electric field, the common electrode CE isformed on the array substrate AR in which the pixel electrode PE isformed.

FIG. 5 is a cross-sectional view schematically showing a structure ofthe array substrate taken along line A-B shown in FIG. 3.

In the array substrate AR, the power supply line CL, the branch wiringLA, and the drawing wiring LB are formed on the first insulatingsubstrate 20. That is, the power supply line CL, the branch wiring LA,and the drawing wiring LB are formed in the same layer as the gate lineG, and can be formed using the same material as the gate line G. Thepower supply line CL, the branch wiring LA and the drawing wiring LB arecovered with the first insulating layer 21.

In the first insulating layer 21, a contact hole CH1 penetrating to theintermediate portion CLM of the power supply line CL, a contact hole CH2penetrating to the one end portion LA1 of the branch wiring LA, acontact hole CH3 penetrating the other end portion LA2 of the branchwiring LA and a contact hole CH4 penetrating to the drawing wiring LBare formed, respectively.

The bridge B1 and the bridge B2 are formed on the first insulating layer21. That is, the bridge B1 and bridge B2 are formed in the same layer asthe source line S and can be formed using the same material as thesource line S.

While the bridge B1 contacts with the intermediate portion CLM throughthe contact hole CH1, the bridge B1 contacts with the one end portionLA1 through the contact hole CH2, and electrically connects the powersupply line CL with the branch wiring LA. While the bridge B2 contactswith the other end portion LA2 through the contact hole CH3, the bridgeB2 contacts with the drawing wiring LB through the contact hole CH4, andelectrically connects the branch wiring LA with the drawing wiring LB.

According to this embodiment, the power supply line CL is arranged alongthe end of the array substrate AR. Moreover, the power supply line CL iselectrically connected with the branch wiring LA arranged between thepower supply line CL and a circuit, for example, the source controlcircuit CC located inside the power supply line CL close to the activearea ACT at the intermediate portion CLM of the power supply line CL.Although the static electricity easily invades from the power supplyline CL located in the circumference of the corner C1 and the corner C2,even if the static electricity invades to the power supply line CL, thestatic electricity is diffused in the power supply line CL, and theenergy of the static electricity is consumed. Moreover, the positionwhere the static electricity flows to inside the power supply line CLbecomes the intermediate portion CLM apart from the position where thestatic electricity invades, i.e., in the circumference of the corner C1and the corner C2. For this reason, during the time when the staticelectricity flows to the intermediate portion CLM, the energy of thestatic electricity is consumed. Therefore, it becomes possible tocontrol flowing of the static electricity with high energy to the wiringor the circuit inside the power supply line CL, or destruction of thewiring and the circuit by the static electricity with high energy.

Moreover, according to this embodiment, the power supply line CL isformed in the shape of a curve at the corners C1 and C2. For thisreason, as compared with a case in which a crooked form of the powersupply line is applied at the corner, the static electricity becomesdifficult to be collected at the curved corner portions. Therefore, itbecomes possible suppress generating of the electric discharge to theinside circuit and the wiring from the power supply line CL near thecorners, or destruction of the inside circuit and the wiring by theelectric discharge.

Moreover, according to this embodiment, the branch wiring LA is equippedwith the first projection P1 projecting toward the power supply line CL.The power supply line CL is equipped with the second projection P2projecting toward the first projection P1. For this reason, the staticelectricity which flows in the power supply line CL concentrates to thesecond projection P2, and it becomes possible to induce the electricdischarge to the first projection P1 from the second projection P2. Thatis, the first projection P1 and the second projection P2 function aswhat is called a lightning rod. By inducing the electric discharge tothe first projection P1 from the second projection P2, the energy of thestatic electricity is consumed, and it becomes possible further toimprove protective operation to the inside circuit or wiring against thestatic electricity.

The first projection P1 and the second projection P2 are formed near thebridge B1 which connects the intermediate portion CLM of the powersupply line CL with one end portion LA1 of the branch wiring LA, and thebridge B2 which connects the other end portion LA2 of the branch wiringLA with the drawing wiring LB pulled out from the source control circuitCC, respectively. By inducing the electric discharge between the firstprojection P1 and the second projection P2 near the bridge B1, itbecomes possible to reduce the energy of the static electricity whichflows into the branch wiring LA from the power supply line CL throughthe bridge B1. Moreover, it becomes possible to reduce the energy of thestatic electricity which flows into the drawing wiring LB from thebranch wiring LA through the bridge B2 by inducing the electricdischarge between the first projection P1 and the second projection P2near the bridge B2. In addition, even if the first projection P1 isshorted out with the second projection P2 by the electric discharge,since the potential of the power supply line CL and the branch wiring LAare the same, they can preserve each function.

Moreover, according to this embodiment, the bridge B1 contacts the powersupply line CL and the branch wiring LA through the contact hole formedin the first insulating layer 21, and the bridge B2 contacts with thebranch wiring LA and the drawing wiring LB through the contact holeformed in the first insulating layer 21. In the bridge B1 and the bridgeB2, it becomes possible to consume the energy of the static electricitywhich flows into the contact holes by adjusting the contact resistivityof the contact hole. For example, the contact resistivity is controlledby adjusting a contact area or a diameter of the contact hole.

In the above embodiment, the source control circuit CC is connected withthe branch wiring LA through the drawing wiring LB. However, othercircuit device can be used in place of the source control circuit CC,and same effect can be achieved.

As explained above, according to this embodiment, it is possible tosupply the liquid crystal display device which can control the staticelectricity defect.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. In practice, the structural and method elementscan be modified without departing from the spirit of the invention.Various embodiments can be made by properly combining the structural andmethod elements disclosed in the embodiments. For example, somestructural and method elements may be omitted from all the structuraland method elements disclosed in the embodiments. Furthermore, thestructural and method elements in different embodiments may properly becombined. The accompanying claims and their equivalents are intended tocover such forms or modifications as would fall with the scope of theinvention.

What is claimed is:
 1. A liquid crystal display device, comprising: a first substrate including an active area in the shape of a rectangle having a first end portion, a second end portion, a third end portion and a fourth end portion surrounding the active area; a second substrate facing the first substrate ; and a liquid crystal layer held between the first substrate and the second substrate; wherein the first substrate includes; a gate line extending in a first direction and a source line extending in a second direction orthogonally crossing the first direction in the active area, a source driver electrically connected with one end of the source lines drawn to the first end portion from the active area, a source control circuit electrically connected with the other end of the source lines drawn to the third end portion from the active area, a first common terminal and a second common terminal of a common potential formed in the first end portion, a power supply line electrically connected with the first common terminal and extending along the second, third and fourth end portions in this order, and connected with the second common terminal, and a branch wiring electrically connected between an intermediate portion of the electric power supply line along the third end portion and the source control circuit, and extending in the first direction.
 2. The liquid crystal display device according to claim 1, wherein a first corner in which the second end portion and the third end portion in the power supply line cross, and a second corner in which the third end portion and the fourth end portion in the power supply line cross are respectively formed in a curved shape.
 3. The liquid crystal display device according to claim 2, wherein the intermediate portion of the power supply line is located substantially in a center portion between the first corner and the second corner.
 4. The liquid crystal display device according to claim 1, wherein the branch wiring includes a first projection projecting to the power supply line, and the power supply line includes a second projection projecting to the first projection.
 5. The liquid crystal display device according to claim 4, wherein the first projection is formed in one end portion and the other end portion of the branch wiring.
 6. The liquid crystal display device according to claim 1, further comprising; an insulating layer covering the gate line, the power supply line, the branch wiring, and a drawing wiring pulled out from the source control circuit, a first bridge formed on the insulating layer and electrically contacted with the one end portion of the branch wiring and the intermediate portion of the power supply line through a first contact hole, and a second bridge formed on the insulating layer and electrically contacted with the other end portion of the branch wiring and the drawing wiring through a second contact hole.
 7. The liquid crystal display device according to claim 6, wherein the first bridge and the second bridge are formed in the same layer as the source line.
 8. A liquid crystal display device, comprising: a first substrate including an active area in the shape of a rectangle having a first end portion, a second end portion, a third end portion and a fourth end portion surrounding the active area; a second substrate facing the first substrate; and a liquid crystal layer held between the first substrate and the second substrate; wherein the first substrate includes; a gate line extending in a first direction and a source line extending in a second direction orthogonally crossing the first direction in the active area, a source driver electrically connected with one end of the source lines drawn to the first end portion from the active area, a source control circuit electrically connected with the other end of the source lines drawn to the third end portion from the active area, a first common terminal and a second common terminal of a common potential formed in the first end portion, a power supply line electrically connected with the first common terminal and extending along the second, third and fourth end portions in this order, and connected with the second common terminal, a branch wiring electrically connected with an intermediate portion of the electric power supply line along the third end portion and the source control circuit, and extending in the first direction, and an insulating layer covering the gate line, the power supply line, the branch wiring, and a drawing wiring pulled out from the source control circuit, and wherein a first corner in which the second end portion and the third end portion in the power supply line cross, and a second corner in which the third end portion and the fourth end portion in the power supply line cross are respectively formed in a curved shape, the intermediate portion of the power supply line is located substantially in a center portion between the first corner and the second corner, the branch wiring includes a first projection projecting to the power supply line, and the power supply line includes a second projection projecting to the first projection, a first bridge is formed on the insulating layer and electrically contacted with the one end portion of the branch wiring and the intermediate portion of the power supply line through a first contact hole, and a second bridge is formed on the insulating layer and electrically contacted with the other end portion of the branch wiring and the drawing wiring through a second contact hole.
 9. The liquid crystal display device according to claim 8, wherein the first bridge and the second bridge are formed in the same layer as the source line.
 10. A liquid crystal display device, comprising: a first substrate including an active area in a shape of a square having a first end portion, a second end portion, a third end portion and a fourth end portion surrounding the active area; a second substrate facing the first substrate; and a liquid crystal layer held between the first substrate and the second substrate; wherein the first substrate includes; a gate line extending in a first direction and a source line extending a second direction orthogonally crossing the first direction in the active area, a source driver electrically connected with one end of the source lines drawn to the first end portion from the active area, a first common terminal and a second common terminal of a common potential formed in the first end portion, a power supply line electrically connected with the first common terminal and extending along the second, third and fourth end portions in this order, and electrically connected with the second common terminal, a circuit device arranged between the third end portion of the power supply line and the active area, and a branch wiring electrically connected with an intermediate portion of the electric power supply line along the third end portion and the circuit device, and extending in the first direction.
 11. The liquid crystal display device according to claim 10, wherein a first corner in which the second end portion and the third end portion in the power supply line cross, and a second corner in which the third end portion and the fourth end portion in the power supply line cross are respectively formed in a curved shape.
 12. The liquid crystal display device according to claim 11, wherein the intermediate portion of the power supply line is located substantially in a center portion between the first corner and the second corner.
 13. The liquid crystal display device according to claim 10, wherein the branch wiring includes a first projection projecting to the power supply line, and the power supply line includes a second projection projecting to the first projection.
 14. The liquid crystal display device according to claim 10, further comprising; an insulating layer covering the gate line, the power supply line, the branch wiring, and a drawing wiring pulled out from the source control circuit, a first bridge formed on the insulating layer and electrically contacted with the one end portion of the branch wiring and the intermediate portion of the power supply line through a first contact hole, and a second bridge formed on the insulating layer and electrically contacted with the other end portion of the branch wiring and the drawing wiring through a second contact hole.
 15. The liquid crystal display device according to claim 14, wherein the first bridge and the second bridge are formed in the same layer as the source line. 